Hull Re-Core on a Fiberglass Sailboat
A while back I was asked to perform a pre-purchase, condition and valuation survey on a fiberglass thirty-five foot sailboat. In all fairness even though the manufacturer is no longer in business I won’t mention their name. Lets just say that it was a Canadian built boat, manufactured in the early eighties and not many were built.
As I usually do I began with an inspection of the hull exterior surfaces starting with the below waterline areas. A visual inspection showed many layers of flaking bottom paint, blisters half the size of my fist and almost every type of bottom issue that you can name. My moisture meter registers its maximum reading at 99 and at that point a red light flashes. The red light was flashing for a good portion of the time and there were very few areas on that I would consider normal moisture levels for a boat of this age. Sounding the hull was more like tapping a hammer on a leather arm chair that a fiberglass boat hull.
To make a long story short the buyer was able to negotiate a very attractive purchase price and the boat was moved to a local fiberglass repair firm for a complete bottom laminate re-core.
The original hull construction was a balsa cored fiberglass sandwich structure which had over time taken on a considerable amount of water. The pictures and text below show the repair process.
This is the hull with part of the exterior laminate layers and the balsa core removed. The edge of the balsa can be seen in near the middle of the photo. The white material is dry fiberglass which is something you should never find inside a fiberglass laminate. It’s obviously been this way since new.
This is some of what was swept up on the floor after the balsa was removed. Lots of black rotten wood and even more dry fiberglass.
This is the bow area with the new balsa core installed. The blue material is a core bonding compound specially formulated to bond the core to the inside fiberglass laminate layers. The gap at the bow will be filled with solid fiberglass and resin. No balsa will be used here.
The new core with the exterior fiberglass laminate layers completed. At this point the hull will be given a preliminary sanding and then the fairing material will be applied.
Now the fairing compound has been applied and next the hull will be sanded smooth in preparation for the final epoxy barrier coat. Next the new fiberglass will be allowed to out gas (cure) before the final epoxy barrier coats and the antifouling are applied. The boat will then be ready for launch
While complete bottom re-core jobs like this are rare, this proves that they can be done. All it takes is money. By the way the price for this job was in excess of 25 K.
Reprinted From “The Seaworthy Surveyor” Ontario Sailor Magazine
Original Article By David Sandford AMS®